Electromagnetic radiation contains intensity, color (wavelength), and polarization information. The human eye and conventional cameras are not polarization sensitive. The polarization parameters of light are orthogonal to the direction of propagation of the light. The state of polarization (“SOP”) from an image is determined from the four Stokes vectors. As the light interacts with objects in the environment, the polarization parameters of light are altered in a fashion directly related to the material composition, surface roughness of objects and shape of the objects. A man-made object has a different polarimetric image than a natural object, for example. Polarization parameters are not affected by color camouflage, fog, or other traditional optical obstructions and so contain important information that can be used in a variety of applications such as military applications, astronomical observation, remote sensing, security surveillance, and terrain avoidance.
In addition to conventional uses of polarized images, miniaturized systems are becoming increasingly important, for example, in medical imaging and surveillance applications. A miniaturized polarimeter could provide diagnostic information in an endoscopic application, for example.
A variety of polarimeters have been developed. Conventional polarimetric instruments require rotating or moving parts to acquire the complete Stokes vectors. Rotating and moving parts require additional control systems, add complexity to the instrument, add mechanical noise and increases risk of breakage. In addition, a rotational or motional scheme requires several measurements to be taken to acquire state of polarization information from the object, limiting measurements to static scenes and slowing frame rates for video acquisition. Some instruments determine state of polarization information from an object by splitting the incident beam into spatially resolved parts determined by the polarization vector, and detecting the different spatial parts separately. These systems have additional complexity, lower resolution, higher cost and other disadvantages.
There is a need in the art for an improved system for providing real-time polarization information, as well as a need for a miniaturized polarimeter.